The present invention provides a defoaming apparatus for continuous operation and an apparatus characterized in a compact unit, a high-defoaming rate and an automatic feed and discharge. Particularly this invention provides outstanding effects in defoaming highly viscous fluids which contain bubbles.
The conventional methods for defoaming liquid material can be fairly divided into two types:
The first method is to subject the liquid material to form a thin-film viscous flow along the surface of a slanting plate and then flowing the same downward in the defoaming cylinder under a very low pressure (Shown in FIG. 1). The slanting plate (101) is set to increase the distance of flow path of fluid which enables the liquid material to flow stagnantly in a form of thin film and bubbles therein to expand and break off under a low pressure so that the objective of the present invention can be achieved. However, there are some disadvantages in such a defoaming method. One of the disadvantages is that they need a very bulky apparatus and also the flow rate of the liquid is very slow. Moreover, a thick liquid layer could easily be created due to an excess feed which would results in an undesirable effect in the defoaming treatment. Another disadvantage is that the machine operations such as air suction and the like must be stopped to take the material out of the apparatus when a considerable amount of the defoamed material has been accumulated at the bottom of the cylinder which causes inconvenience in the continuous operation. The second method makes use of a stirrer (Shown in FIG. 2). Material is charged in a closed vessel and stirred with a fan-shaped stirrer (102) under low pressure, which causes bubbles to expand and rise up to the surface of the liquid and flee away and therefore the purpose of defoaming is achieved. However, there are some disadvantages in such a method: the volume of said vessel is too large, the defoaming rate is too slow and the defoaming effect, usually, is not satisfactory; particularly, the defoaming effect can not be completed at the defiladed space where the stirring fan does not reach. Furthermore, bubbles may never break off even they have expanded when the fluids with high viscosity are stirred at the upper portion of said fan because the surface tension of the bubbles is sufficient to compete with the pressure difference between the inner and outer pressure of bubbles. This causes a soap foam like materials floating over the upper layer of the liquid. Accordingly, this method cannot provide a satisfactory defoaming results for highly viscous fluids.